Guanethidine Tablets

Action and use

Adrenergic neuron blocker.

Definition

Guanethidine Tablets contain Guanethidine Monosulfate.

Content of guanethidine monosulfate, C₁₀H₂₂N₄,H₂SO₄

90.0 to 110.0% of the stated amount.

Identification

Extract a quantity of the powdered tablets containing 50 mg of Guanethidine Monosulfate with a mixture of 5 mL of hydrochloric acid and 45 mL of water, filter, neutralise 25 mL of the filtrate with 5m sodium hydroxide and add 20 mL of picric acid solution R1. The melting point of the precipitate, after washing with water, is about 153°, Appendix V A.

Assay

Weigh and powder 20 tablets. Shake a quantity of the powder containing 30 mg of Guanethidine Monosulfate for 15 minutes with 50 mL of water, dilute to 100 mL with water and filter. To 5 mL of the filtrate add 10 mL of a solution prepared by dissolving 1 g of sodium nitroprusside and 1 g of potassium hexacyanoferrate(II) in 50 mL of a 0.5% w/v solution of sodium hydroxide, adding 5 mL of hydrogen peroxide solution (100 vol), swirling gently and diluting to 100 mL with the solution of sodium hydroxide. Mix, allow to stand for 20 minutes, add sufficient water to produce 25 mL and measure the absorbance of the resulting solution at 520 nm, Appendix II B, using in the reference cell a solution prepared by treating 5 mL of water in the same manner, beginning at the words ‘add 10 mL of a solution…’. Repeat the operation using 5 mL of a 0.03% w/v solution of guanethidine monosulfate BPCRS beginning at the words ‘add 10 mL of a solution …’. Calculate the content of C₁₀H₂₂N₄,H₂SO₄ in the tablets from the absorbances obtained using the declared content of C₁₀H₂₂N₄,H₂SO₄ in guanethidine monosulfate BPCRS.

Storage

Guanethidine Tablets should be protected from light.